The present invention relates to solvent resistant vulcanizable silicone rubber compositions, and more particularly, the present invention relates to an improved two-component room temperature vulcanizable silicone rubber composition having fluorinated substituent groups in the polymers which are cured in the presence of a platinum catalyst to form a solvent resistant elastomer.
Silicone elastomers are well known in the art and are used for many applications in which high and low temperature stability are desired.
One class of solvent resistant room temperature vulcanizable silicone rubber compositions is disclosed and claimed in U.S. Pat. No. 4,041,010 which is incorporated herein by reference. The solvent resistant room temperature vulcanizable silicone rubber compositions disclosed and claimed in U.S. Pat. No. 4,041,010 comprise: (A) 100 parts of a mixture composed of (i) 100 parts of a vinyl-containing polymer of the formula, ##STR1## where Vi is vinyl, R is selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms and phenyl, R' is perfluoroalkyl of 1 to 8 carbon atoms, x an y are at least 1 and the viscosity of the compound varies from 1,000 to 500,000 centipoise at 25.degree. C., and the concentration of siloxy units taken y times varies from 5 to 98 mole pecent; (ii) from 1 to 60 parts of a vinyl-containing resin selected from the class consisting of a resin having ViRR"SiO.sub.0.5 units and SiO.sub.2 units where the hydrocarbon substituent to Si ratio varies from 0.8 to 2.7; a resin having ViRR"SiO.sub.0.5 units, SiO.sub.2 units and RR"SiO units where the hydrocarbon substituent to Si ratio varies from 0.8 to 2.4; a resin having ViR.sub.2 SiO.sub.0.5 units, R.sub.2 R"SiO.sub.0.5 units, SiO.sub.2 units and RR"SiO units where the hydrocarbon subsituent to Si ratio varies from 0.8 to 2.4; and a resin having R.sub.2 R"SiO.sub.0.5 units, SiO.sub.2 units and ViR"SiO units where the hydrocarbon substituent to Si ratio varies from 0.8 to 2.4, where Vi and R are as previously defined, R" is selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms, phenyl radicals and --CH.sub.2 CH.sub.2 R' radicals, where R' is as previously defined and the vinyl concentration of said resin must not differ more than 20 mole percent from the vinyl concentration of polymer (i); (iii) from 0.1 to 50 parts per million of the total composition of a platinum catalyst; and (B) from 1 to 50 parts based on 100 parts of the mixture of (A) of a cross-linking polymer selected from the class
consisting of (iv) a resin having ##STR2## units and SiO.sub.2 units where the R+R"'+H to Si ratio varies from 1.0 to 2.7; (v) a resin having ##STR3## units, SiO.sub.2 units and RR"'SiO units where the R+R"'+H to Si ratio varies from 1.2 to 2.7; and (vi) a polymer of the formula ##STR4## and mixtures thereof and where the concentration of the units taken t times varies from 0 to 75 mole percent, where R and R' are as previously defined, s is at least 1, t and z may be zero or a positive integer, and the viscosity of the polymer varies from 10 to 1000 centipoise at 25.degree. C., and R"' is selected from the class consisting of alkyl radicals of 1 to 8 carbon atoms and --CH.sub.2 CH.sub.2 R' radicals.
The foregoing compositions described and claimed in U.S. Pat. No. 4,041,010 overcome many prior art deficiencies by having proper solvent resistance to hydrocarbon fluids, good physical properties and a fast cure rate at elevated temperatures even though the compositions are SiH-olefin platinum catalyzed silicone rubber compositions having fluorinated substituent radicals.
Although the elastomers of U.S. Pat. No. 4,041,010 have good elastomer properties, it is desirable to improve the properties of the elastomers for various uses. For example, it is desirable in certain instances to improve the tensile strength-elongation properties of silicone elastomer products of the SiH-olefin platinum catalyzed silicone rubbers having fluorinated substituent radicals without affecting the solvent resistance of the silicone rubber composition to hydrocarbon fluids and without substantially affecting the cure rate at elevated temperatures.